1. Field of the Invention
The invention generally relates to joint structures and methods for forming joint structures that are ideally suited for use in a vehicle body-in-white. More specifically, the invention provides both a friction welded joint assembly in which lineals and sheet, cast or extruded components are joined together and a structure and method for improving the stability of the joint structure.
2. Description of the Prior Art
It is known that various structural components for automobiles and other vehicles can be made from aluminum and other light metal alloys. Considerable development work is now underway with an objective of utilizing aluminum and other light metal alloys in the primary body structure of a vehicle or, as it is often called, the “body-in-white.” An automobile chassis or body-in-white comprised of light metal alloys weighs considerably less than a steel frame that has been designed to satisfy the same requirements of safety and durability. A vehicle utilizing such a body-in-white produced from light metal alloys has improved fuel efficiency without sacrificing performance. Moreover, if the alloy utilized is an aluminum alloy, it is more easily recycled than a steel frame vehicle, and it offers improved corrosion resistance. In addition, it is known that a body-in-white utilizing space frame technology will distribute and absorb the forces encountered in the normal operation of an automobile as well as absorb and dissipate the energy of a crash or rollover.
By way of brief explanation, the space frame is a latticed framework of structural beams and columns that are joined together at their ends. These structural components of the space frame, which are sometimes referred to as lineals, are connected together by mechanical means such as bolts, rivets and clinches, by welding and adhesive bonding, and by a combination of the afore described methods. Another method for connecting the lineals of a space frame is by the use of separate joining components or connecting members which are often referred to as “nodes” into which the lineals are designed to fit. The lineals are then securely attached to the nodes by any of the known connecting methods referred to above. An example of this technology is found in U.S. Pat. No. 4,618,163 which pertains to an automobile chassis that includes lineals and nodes. This patent is incorporated herein by reference as if fully set forth herein. If the lineals are to be joined by means of connecting members or nodes, the nodes are typically cast or otherwise formed in a separate manufacturing operation. If the lineals are to be mechanically attached to each other or to nodes by means of bolts or other fasteners, appropriate holes must be provided in the several components. In the alternative, or in addition, welding, soldering, or adhesive bonding equipment and materials may be required to effect the joining of the components. Furthermore, the tolerances of the various components that are to be assembled together must be exact in order for holes to align with other holes or with protrusions or in order for the surfaces to fit together for welding, soldering or adhesive bonding. Finally, the complete frame is assembled in a series of discreet steps involving the joining of individual lineals to nodes or to other lineals or components in order to form subassemblies and then the subsequent joining of the various subassemblies to form the entire body-in-white space frame. As noted above, U.S. Pat. No. 4,618,163 to Hasler et al., describes an automobile space frame chassis that is made from a plurality of tubular light metal lineals that are held together by connecting members also made from light metal. Hasler et al. discloses the use of tubular members assembled by inserting their end sections into recesses in the connecting or receiving members. However, this technique has the disadvantage that the last member to be mounted in an assembly or subassembly could only be mounted by flexing or bending the structure. The elongated frame members of Hasler et al. are secured to the connecting members by welding, soldering or cementing or by the use of mechanical fasteners such as bolts, screws, and rivets.
U.S. Pat. No. 5,381,849 to Fussnegger et al. discloses a method for casting a connecting member onto the end of a hollow section such as an extruded aluminum frame member. According to this method, an end of the hollow section is placed in a mold with the end of the hollow section closed with a plug to prevent penetration of cast material therein. This method is not used to join extruded frame parts to each other but rather to join them to a cast frame member. These cast frame members are complicated solid structures that are formed in complicated molds. In addition, because the Fussnegger et al. castings may be of considerable size, they may add considerable weight to the frame structure formed by this method. It clearly is desirable to join together the components of a space frame by a simple process that minimizes manufacturing steps, compensates for tolerances at the joints, and is economical to implement.